In the past, box spring foundations comprised a pair of generally rectangular border wires which were spaced apart by coil or bent wire spring modules. A problem with such earlier designs is that they are bulky to ship to a bedding manufacturer for securement to a slat base and the application of padding and covering. The bulkiness results from having an open wire structure with no capability of nestable stacking.
Early foundation designs were resiliently collapsed (compressed) for shipping and held in the collapsed state with ties. This however required both the application and removal of ties which is both time consuming and wasteful. Furthermore, such a degree of resiliency may be undesirable at least in some applications.
In order to avoid having to compress and restore a foundation, later designs provided for either nestably stackable configurations or hingedly collapsible arrangements. U.S. Pat. Nos. 5,346,188 to Rodgers et al and 5,622,357 to Schulz Jr. et al are examples of a folding arrangement. U.S. Pat. Nos. 6,484,339B2 to Mossbeck et al and 5,967,499 to McGraw et al are examples of the latter arrangement.
The foregoing designs each have shortcomings. The hingedly collapsible arrangements tend to be more complex as hinging must be provided to enable collapse. Once erected however hinging is no longer desirable as it affects the inherent lateral stability of the design. Some of the nesting designs have complicated (and therefore more difficult and costly to manufacture) support elements. Others are less laterally stable than might be desirable. Still others have relatively labour intensive attachment arrangements for connecting the structural elements.
Objects of the present invention include providing a nestably stackable box spring foundation which is simple to manufacture, cost effective and robust.